Dunphy v. Ryan was a United States Supreme Court case that dealt with the issue of whether a state court had the authority to issue a writ of habeas corpus to a prisoner who was being held in a federal prison. The case arose when a prisoner, John Dunphy, was held in a federal prison in New York. Dunphy sought a writ of habeas corpus from the New York state court, claiming that he was being held in violation of his constitutional rights. The federal government argued that the state court did not have the authority to issue the writ, as the federal government had exclusive jurisdiction over federal prisons. The Supreme Court ultimately held that the state court did have the authority to issue the writ of habeas corpus. The Court reasoned that the writ of habeas corpus was a fundamental right that could not be denied by the federal government. The Court also noted that the writ of habeas corpus was a necessary tool to ensure that prisoners were not held in violation of their constitutional rights. As such, the Court held that the state court had the authority to issue the writ of habeas corpus to Dunphy.

Justice Field delivered the dissenting opinion in Dunphy v. Ryan, arguing that the majority had misinterpreted a key provision of the California Civil Code and failed to consider relevant case law from other states. He argued that under California's code, an executor was not liable for debts incurred by their predecessor unless they expressly assumed them or were otherwise legally obligated to pay them. Furthermore, he noted that courts in other jurisdictions had held similar views on this matter and found no liability against executors who did not assume such obligations. In conclusion, Justice Field believed that there was insufficient evidence to hold Dunphy liable for his predecessor's debt and thus should be absolved of any responsibility for it.